The ability of plastic films to retain inks, coatings, adhesives, etc., is primarily dependent on the character of their surfaces, and can be improved by one of several surface-treatment techniques. These same treatment techniques have been found to increase the wetting tension of a plastic film surface in contact with mixtures of solvents. It is therefore possible to relate the wetting tension of a plastic film surface to its ability to accept and retain inks, coatings, adhesives, etc. The measured wetting tension of a specific film surface can only be related to acceptable ink, coating, or adhesive retention through experience. Wetting tension, in itself, is not a completely acceptable measure of ink, coating or adhesive adhesion.
The test is not applicable when the surface of the material to be tested reacts chemically with the test solution.